It's just that, since the result seemed to be "bit-perfect"... it didn't seem logical to me (and honestly, it still doesn't...).
So, there really isn't any locked and protected "bit-perfect" output solution (I'm an idiot because it was already obvious if you consider the range of output levels)
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If I may share my opinion, the importance of "bit-perfect" is greatly exaggerated these days.
What I'll say next may be counter-intuitive to many people, but I'm fully convinced of it: attempting to go "bit-perfect" can actually degrade the quality of one's audio!
Let me try to explain my position:
With devices that offer high bit-depth volume controls (I believe WiiM use 32-bit, which is a a lot!) there's no degradation to the original signal and no increase in digital noise when decreasing volume digitally. It isn't "bit-perfect" anymore, but it is "perfect" in any meaningful sense.
On the other hand, analogue volume controls can introduce audible imperfections like volume mismatch or crackling (when potentiometers become scratchy). So in summary, with high SNR devices that have high bit-depth volume controls I truly see really no point in trying to override the digital volume control.
In addition, when you set your device for "bit-perfect" playback, with fixed volume (and volume limit to 100%) you actually increase the risk of running into inter-sample overloads and digital clipping in general - especially with loud mastered recordings. This effectively (and unnecessarily) decreases the sound quality. There's IMHO really no need to demand DACs to have huge inter-sample overload headroom when we can just decrease the digital volume by a few dB, without any loss in audio quality whatsoever.
Lastly, "bit-perfect" also implies that all DSP (EQ, RoomFit, Bass Management...) has to be disabled.
Given that optimally configured EQ, RoomFit and Bass Management can each significantly improve sound quality in most environments, that puts the last nail in the "bit-perfect" coffin, at least in my book.
To summarize - it seems to me that many users run themselves into a corner trying to chase "bit-perfect", and then they have to search for solutions to the various problems this can bring. But these problems can be avoided altogether by recognizing that "bit-perfect" is not really a necessity for "perfect" sound quality (anymore).
Digital volume controls are convenient and transparent, plus having the volume significantly below 100% avoids issues like inter-sample overload and digital clipping altogether.
No automatic gain in the correction modes... fixed levels... limits... but also input level presets, etc.
It's incredibly confusing...
especially since there's no "fair" observation of the levels, with a DRC...
Too much...or for ""expert""
I fully agree with you that advanced WiiM device configuration is quite complex, and not really intuitive.
It seems to me this could probably be improved with a significant UI/UX redesign.